Answer:
1. An apple is something that has matter.
2. Light does not have matter. It neither has mass or takes up and space.
3. Physical changes only change the appearance of a substance, not its chemical composition. Chemical changes cause a substance to change into an entirely substance with a new chemical formula. Chemical changes are also known as chemical reactions.
4. A chemical reaction is usually accompanied by easily observed physical effects, such as the emission of heat and light, the formation of a precipitate, the evolution of gas, or a color change. Absolute confirmation of a chemical change can only be validated by chemical analysis of the products!
5. A precipitate is a solid that forms out of solution.
6. In simple terms, the endothermic reactions absorb energy from the surrounding that is in the form of heat. On the other hand, an exothermic reaction releases energy into the surrounding of the system.
Explanation:
Matter is anything that has mass and takes up volume.
Answer: 35 grams
Explanation: In sea water there is typically close to 35 grams of dissolved salts in each liter. It is written as 35 ‰ The normal range of ocean salinity ranges between 33-37 grams per liter (33‰ - 37‰). But as in weather, where there are areas of high and low pressure, there are areas of high and low salinity.
Answer: C
Explanation: Picture attached.
Answer:
I do believe it is A
Explanation:
As we grow older, our hearing system gets weaker causing our hearing to go off.
Answer:
The answer is B on edge
Explanation:
Here are my notes on this section for anyone that needs them
Enthalpy and State Function
Bonds contain potential energy. Breaking and forming bonds involves energy. Reactants and products contain energy. Enthalpy (H) is a measure of heat and internal energy in a system.
A state function is a quantity whose change in magnitude during a process depends only on the beginning and end points the process, not the path taken between them. Enthalpy change during reaction depends only on the identity of reactants and products and their initial and finial condition
Enthalpy of Formation
enthalpy of formation (Hf) is the energy absorbed or released when a pure substance forms from elements in their standard states
Units: kJ/mol, kcal/mol
Standard state is the natural state of an element at 1 atm (atmosphere of pressure) and 25 degrees celsius. Hf for a pure element in its standard state is 0 kJ/mol.
H (hydrogen): H2(g)
N (nitrogen): N2(g)
O (oxygen): O2(g)
F (fluorine): F2(g)
Cl (chlorine): Cl2(g)
Br (bromine): Br2(l)
Hg (mercury): Hg(l)
Enthalpy of Reaction
Enthalpy of reaction (Hrxn) is energy absorbed or released during a chemical reaction
Hrxn negative: exothermic reaction
Hrxn positive: endothermic reaction
Hess's Law: Hrxn = Σ(ΔHƒ, products) − Σ(ΔHƒ, reactants)
thermochemical equation: the chemical equation that shows the state of each substance involved and the energy change involved in a reaction
Find the kJ/mol of the product and then subtract the kJ/mol of the reactants.
