chemical change
Cards (39)
- reactant = starting material
- What is the law of conservation of mass?Atoms are not created or destroyed in a chemical reaction
- In the reaction metal + acid -> salt + hydrogen, why does the mass decrease?Atoms are being lost as a gas
- In the reaction magnesium + oxygen -> magnesium oxide, why does the mass increase?Atoms from a gas (oxygen) are being added
- What is a symbol equation?A chemical equation in which the chemicals are represented by formulae
- What is a balanced equation?A symbol equation where all the reactant atoms have become product atoms
- What do “big numbers” in front of the formula tell us?How many lots of each formula there is in the balanced equation
- Which numbers can be changed when balancing an equation?Big numbers in front of formulae
- How can you tell if an equation is balanced?Equal numbers of atoms of each element on each side of the reaction arrow
- Unit and symbol for mass?Kilogram/kg or gram/g
- Unit and symbol for volume?cubic decimetre/dm3
- What is concentration?The amount of solute dissolved per unit volume of solvent
- Unit and symbol for concentration (when using mass)?Grams per cubic decimetre – g/dm3
- What must particles do in order to have a chance to react?Collide (with sufficient energy and in the correct orientation)
- What is rate of reaction?How quickly a reaction takes place
- Units and symbols for rate?Cubic centimetres per second (cm3/s) & grams per second (g/s)
- How can you monitor rate of reaction?How quickly a product is formed or a reactant is used
- How can you measure how quickly a product is formed?Volume of gas per second using a gas syringe, change in mass
- How can you measure how quickly a reactant is used?Change in mass
- What is turbidity?Cloudiness
- How can you monitor changes in concentration to measure rate?Changes in colour or turbidity (disappearing cross)
- How can you calculate relative rate from time taken?relative rate = 1/time taken
- On a graph of concentration/mass/volume of gas against time, what is represented by the gradient?rate of reaction
- What are the 5 factors that can alter the rate of reaction?Temperature, surface area, pressure (gases), concentration and catalyst
- How does temperature affect rate of reaction?Increasing temperature increases rate of reaction
- What needs to happen to collisions between particles to increase rate?Increased frequency and/or increased energy
- How do particles behave at higher temperatures?They move faster and collide more frequently
- What do particles have more of at higher temperatures?Energy
- Which state of matter can we alter the pressure of?Gases
- How does pressure affect rate of reaction?Increasing pressure increases rate of reaction
- How are particles spaced at high pressure?Closer together – more particles per unit volume.
- How does concentration affect rate of reaction?Increasing concentration increases rate of reaction
- How are particles spaced at low concentration?Further apart – fewer particles per unit volume.
- What effect does breaking solid matter into smaller bits have on surface area?Increases surface area to volume ratio.
- How does surface area affect rate of reaction?Increasing surface area increases rate of reaction
- Why does a larger surface area increase rate of reaction?More particles at the surface and available for collisions
- What is activation energy?The minimum energy with which particles must collide in order to have a successful collision.
- What is a catalyst?A chemical that increases the rate of a reaction without being used up itself
- How do catalysts increase the rate of reaction?By decreasing the activation energy